Tamper-proof window units for use in steel doors and the like have been available in the past and have been generally satisfactory. Such units, however, have normally employed tamper-proof bolts which have not always wholly obviated tampering and which have required drilling through the steel doors adjacent the window openings, providing hole layouts or templates to align door and window frame holes and, in the case of U.L. labelled fire doors, pre-drilling at the factory prior to shipment has been required. Still further, maintaining the parts of the window frame and the associated pane of glass in desired relative positions during shipment and installation has proven unwieldy and somewhat inefficient.